“You should get a group picture and send it to your parents,’’ he grumbled at them. He was displeased with the signs they held, which he found offensive; one referred to folks like him with a derogatory sexual term. He blamed the youthful flippancy on a lack of critical thinking and genuine knowledge as to how the world works. “They don’t understand what socialism means. They don’t understand what democracy means.’’

But it’s not that the youngest voters don’t know what socialism means. It’s that most aren’t scared of it — and find it bizarre that, decades after the fall of the Berlin Wall, a political movement would center itself around opposition to it. The fact that both the tea party and the Republican Party have made vociferous opposition to “socialist’’ policies a key part of their rhetoric helps explain the tepid response among young adults.

Republican strategists see short-term advantages in the tea party movement’s passion. But if conservatives can’t wean themselves off of Cold-War-era rhetoric, they risk alienating an entire generation of young people. The tea party is well on its way to doing just that. A recent New York Times/CBS News survey found that three-quarters of the movement’s supporters were older than 45.

Behind the main crowd at the Boston Common rally, counter-protesters and protesters mixed and argued amidst a carnival-like atmosphere that included costumed provocateurs and what felt like every fringe group in the state handing out pamphlets. But younger attendees expressed skepticism about the tea party message.

Naveed Easton, a 19-year-old Emerson student, said he thought the group was out of touch. “You can notice the shift in society over the past 30 years,’’ he said. “It’s just getting more and more open-minded, and some people are just very resistant to a progressive society. Especially when it comes to, like, ‘Oh, that’s a socialist program!’ ’’

And if the health care reform bill actually were socialist? He shrugged off that concern. “Socialism itself isn’t terrible,’’ he said, unless it involves the abrogation of individual rights.

Easton is just one college student, of course — a liberal one in a liberal town. But his views are far from radical among his peers. A year ago a Rasmussen Reports poll found that Americans under 30 are essentially equally divided on whether socialism or capitalism is a superior economic system.

This may shock those who lived through the Cold War, but there’s nothing irrational about it. Young people grew up in a post-Soviet world. When they hear “socialism,’’ they think Scandinavia, not Russia. They’re much more likely to be struggling with student-loan or credit-card bills than to have been affected one iota by the sort of government overreach that can be credibly tied to socialism.

Conservatives can continue beating the dead horse of socialism. But if they want to finally build a youthful infrastructure they should heed the lesson of Wednesday’s rally. The graying tea party throng cheered wildly when Sarah Palin took the stage; the younger spectators stood around the edges of the crowd — looking unimpressed.